O2 fan increasing temps?!

Hello RIU!

I'm starting my first grow, and I just xfered from jiffy -> ffof and perlite (roughly 70/30). My concern right now is temps in the box. It's a 36x26x19 box lined with 6mil black/white poly. Got two holes, one for intake one for exhaust. Exhaust fan I'm using S&P TD100 inline fan hooked up to 4x8 phresh filter. I also added a 45 cfm to the end of my ducting to help out the td100 cause it seemed like the cf was restricting a lot of air flow. Not quite sure how efficient it is but temps settled down to 80F-83F with the 150w HPS running. Intake is a 45 cfm computer fan. So I'm sure you need circulation of air flow in the room right? So I got myself a 5" O2 fan for circulation, and I thought by adding that it would REDUCE the temps but it climbed up to about 85F~. My first thought was maybe just more space taken up which would lead to higher temps? (fans only 5" so its pretty compact). Anyone have any insight?

And one other thing about temps, it may sound stupid but I feel like I must know. So I measure temps regularly and the way my box is set up, the HPS is more or less in the center of it. So when I put my thermometer on the pot next to my plant, it gets around 83-84. But when I put my thermometer anywhere else in the box, temps are around 79F ish. Is this normal? Should I be worried? Thanks a lot in advance.

ONE last thing! I'm actually very new to gardening, and I transplanted today into FFOF, and I have a one gallon fabric pot, and to pre-water before transplant I put maybe one quart of distilled water? It seemed to be dripping a nice amount at the bottom so I stopped. Did I just flush out my nutes in the ffof?
EDIT: Was more like two quarts o.o

Again, any help would be great!

Temps can and do climb with circulation fans when they are in small spaces. The heat that would travel upward through the topside exhaust opening would be spread around with such a fan instead of just going upward and away from the lower canopy. Figure out how to connect the exhaust intake side to the light hood. Sometimes you can just get a 4-1/2" hole saw with arbor and drill through the side of any grow light to make that opening (exactly what I did ).

Then get a 4" galvanized starting collar (for flex duct) put it in that hole in the side of the hood and connect a piece of flex to your exhaust fan. Use a wye fitting to connect the hole above the cabinet and the hood.Hard to avoid any bends but try to keep the ducting as straight as possible. Also drill a 4-1/2" hole through the top of the cabinet above the fixture (in a way that you may also try to eliminate the circulation fan (not the exhaust fan) altogether by making all intake air for the cabinet come up through a perforated reflective foamboard floor. This bottom to top venting method will preclude the need for the oscillating fan just as long as the exhaust fan is adequate.

In other words, just make the air come up through roughly 1,000 1/4" holes (equidistant) through an intermediate foamboard floor placed between the bottom of the cabinet and just above where the main stems arise from either your soil pots or hydro bin. Your yield will also improve tremendously and it is such an easy thing to implement in a small cabinet. Just think... Do you want the heat to roll around unevenly before it exits the cabinet or would you rather turn the cabinet into the equivalent of a rectangular duct with the air flowing from bottom to top (bottom to top airflow is the most ideal in HVAC theory).

Unconventional? You bet.

contraptionated said:

Temps can and do climb with circulation fans when they are in small spaces. The heat that would travel upward through the topside exhaust opening would be spread around with such a fan instead of just going upward and away from the lower canopy. Figure out how to connect the exhaust intake side to the light hood. Sometimes you can just get a 4-1/2" hole saw with arbor and drill through the side of any grow light to make that opening (exactly what I did ).

Then get a 4" galvanized starting collar (for flex duct) put it in that hole in the side of the hood and connect a piece of flex to your exhaust fan. Use a wye fitting to connect the hole above the cabinet and the hood.Hard to avoid any bends but try to keep the ducting as straight as possible. Also drill a 4-1/2" hole through the top of the cabinet above the fixture (in a way that you may also try to eliminate the circulation fan (not the exhaust fan) altogether by making all intake air for the cabinet come up through a perforated reflective foamboard floor. This bottom to top venting method will preclude the need for the oscillating fan just as long as the exhaust fan is adequate.

In other words, just make the air come up through roughly 1,000 1/4" holes (equidistant) through an intermediate foamboard floor placed between the bottom of the cabinet and just above where the main stems arise from either your soil pots or hydro bin. Your yield will also improve tremendously and it is such an easy thing to implement in a small cabinet. Just think... Do you want the heat to roll around unevenly before it exits the cabinet or would you rather turn the cabinet into the equivalent of a rectangular duct with the air flowing from bottom to top (bottom to top airflow is the most ideal in HVAC theory).

Unconventional? You bet.

Click to expand...

sorry its kinda hard to see. I guess I can't crop pics -.- lol. If I try to link it, the pic comes out sideways? Idk, anyways. Contraptionated, I'm sorry to say, but I'm not much of a DIY guy as you can see, and almost none of that stuff made sense to me without a visual =/. I kinda get what you're saying but at the same time not.

So where would I be drilling the 1/4" holes exactly? And would these holes hinder my CF's job in anyway leaking out odor? And my space that I'm working with is extremely limited if you can't tell in the picture. I can BARELY fit my fan/filter and HPS light. Ducting is bent more than I'd like but right now with the 150w HPS and 23w CFL and all the fans running, the temp on the ground of the box is 80F~ and the thermometer right on the soil reads 87F, but I'm guessing it's b/c the CFL is like three inches away from it.

And are you saying drill a 4" hole on my grow light? I have a 4" hole cutter, but idk if it'll be able to cut through the fixture cleanly without damaging the ballast. (Built in ballast). So basically making a sort of cooltube?

Both my 4" holes are on the back of the cab, the lower one with a case fan pushing cool air into the cab, and the 4" on top connected with ducting to my fan/cf combo. If the hole drilling was possible, could I just drill the 4" hole on the ballast area, and hook some ducting to it and drill a 4" hole on the side perhaps (to the left) and put another case fan attached to the ducting? Sorry if it doesn't really make sense, I'm having one of those "visual" moments lol

I just raised the CFL fixture ever so slightly, and temps went down to 83F. My plan is once I get my hands on couple bigger fixtures, I plan to veg the autos for however short that will be with two 65w CFLs and switch to the HPS afterwards for some peace of mind, and save a little money as well.

Another question, just how much air do you need circulating around? And is there a chance that the added airflow from the mini clip fan would cancel out the negative pressure to prevent odor?

Sorry I know there's a million questions, but tryna get this right.

How much is the max cfm output of the td100 fan? You would be best advised to get rid of the booster fan and increase the size of the duct on the outflow side of the exhaust fan so that the max cfm output of the fan can be achieved. This would work better than putting a booster fan inline with the exhaust whether or not the booster is less or more powerful than the td100. Look up the youtube video for "ACCA Manual D" or read a copy of it on scribd. This will give you an idea of what size duct to use on the effluent side (outflow or sometimes called the return) of your exhaust fan so that it can put out the cfm on the label.

For example: If I want an 8" can fan to suck hot air out of a 1000 watt hood (whether it is enclosed in glass or not) at peak cfm (8" can fans suck out about 750 cfm max) then I need to increase the size of my duct on the return side of the fan to about 12" or maybe even 14" if I have a little offset bend in the line. The fan would also need to be attached directly to the hood on the influent side with no duct between the exhaust fan and the hood to achieve something very close to the max cfm listed on the fan. That's just an example to illustrate how the duct must be larger than the diameter of the exhaust fans return side to achieve max heat extraction. Now go checkout ACCA Manual D and apply what you learn to your cabinet. Start by looking for the list of round flexible ducts and their max cfm capabilities at various static pressures. Make sure you understand how to calculate the available static pressure in your system, after you're done reading the manual for a few days.

Now remember this: Even if you do become an HVAC EXPERT after reading the ACCA Manual D just don't make the exhaust fan put out so much air that you don't get enough contact time with the carbon in your filter. You only want to achieve the max cfm allowable by the spec sheet of your carbon filter, otherwise you will be overly successful in removing heat and leaking odors. The bottleneck for airflow is the minimum contact time needed for sufficient odor removal. You might need to buy a larger carbon filter and put it in an auxiliary cabinet if this is the case (if you need more airflow and a small carbon filter becomes ineffective).